A wireless fidelity (WiFi) technology is a main technical standard of a wireless local area network (WLAN). The technical standard 802.11 formulated by the Institute of Electrical and Electronics Engineers (IEEE) is technically mature after developing into various versions such as 802.11a, 802.11b, 802.11d, 802.11n, and 802.11ac, and a transmission speed is increasingly higher. In another aspect, due to specific flexibility of the WiFi technology, the WiFi technology is widely applied in household and commercial environments. In a WiFi-based WLAN network, a receiver performs a baseband processing procedure on a received signal, mainly including: symbol synchronization, channel estimation, and data preprocessing. The symbol synchronization refers to performing symbol synchronization according to a received short training field (STF) and the received signal to implement frequency synchronization and time synchronization between a transmitter and a receiver. The channel estimation actually uses a received long training field (LTF) to perform channel estimation so as to obtain channel information. The data preprocessing actually refers to performing channel equalization on a signal according to the channel information obtained by means of the channel estimation, so as to eliminate channel impact.
In a multiple-input multiple-output (MIMO) scenario of uplink multiple users, that is, in a scenario in which one access station and at least two stations are included and the access station includes at least two antennas, each station multiplies an LTF by a preset pilot coefficient corresponding to each symbol period on a per-subcarrier basis on the subcarrier of each symbol period in each symbol period of N consecutive symbol periods, and sends the STF to the access station on the subcarrier in each symbol period. A quantity of the at least two stations is N. A frequency deviation between each different station and the access station makes a phase deviation of the transmitters increase over time.
If the access station directly performs channel estimation according to the pilot coefficient corresponding to the subcarrier of each station, the frequency deviation leads to low precision of the channel estimation.